• Trees are a special case of a graph data structure. The connections radiate out from a single root without cross connections.
• The tree has nodes (shown with circles) that are connected with branches. Each node will have a parent node (except for the root) and may have multiple child nodes.
• In an unordered tree the children of a node can be unordered, however in an ordered tree the children take priority, often by listing them in order.
• A Boolean tree applies operators for each of the nodes